The non-metal used in the purple coloured solution applied on wounds as…

Different non-metals and halogens have characteristic colours and physical states, and a solution's colour together with its chemical (oxidising/germicidal) behaviour when dissolved in a solvent is what determines whether it is suited to a particular practical use, such as a topical antiseptic.

Iodine is a non-metal (halogen) that occurs as a dark, violet-black crystalline solid. When dissolved in ethyl alcohol along with potassium iodide, it forms “tincture of iodine” — a solution conventionally described (as in this question) as purple-tinted, though shades can range to reddish-brown depending on concentration. This solution has strong disinfecting (germicidal) action, which is why it is the standard antiseptic applied on cuts and wounds.

Checking this against the other halogens/non-metals confirms the choice: chlorine is a pale greenish-yellow gas used mainly to disinfect water and as a bleaching agent, bromine is a reddish-brown fuming liquid, and sulphur is a yellow solid — none of these gives the purple-tinted wound-antiseptic solution that iodine's alcoholic tincture does, so Iodine is the correct answer.